In this study, indium-tin-oxide (ITO) films were used as p-contacts in GaN-based light-emitting diodes (LEDs). The dependence of the optoelectronic performance of LEDs on various annealing temperatures of ITO films was studied. At an annealing temperature of 600 degrees C the transmittance of ITO films can reach 98.6% at a wavelength of 470 nm. The specific contact resistance characterized by the circular transmission line model is as low as 7.73x10(-3) Omega cm(2). Furthermore, GaN-based LEDs employing an ITO p-contact annealed at 600 degrees C have high luminescence intensities of 243.2 mcd at a 20 mA injection current. Under the same injection current, the proposed LED also has the largest electroluminescence intensity with the ITO p-contact annealed at 600 degrees C. (c) 2007 The Electrochemical Society.